Distributed Robust Secondary Frequency Control of Inverter-Based Microgrids Under Time-Varying Communication Delays

This paper presents a robust secondary control strategy for frequency synchronization and active power sharing for inverter-based microgrids. The problem is addressed in a multi-agent fashion where the local controllers of the distributed generators play the role of agents, and communication is affected by time-varying delays. The approach is fully distributed and based on a synergic combination of linear consensus and integral sliding-mode control. Lyapunov analysis is presented to assess the stability properties of the closed loop. Delay-dependent stability conditions are expressed as a set of linear matrix inequalities whose solution yields appropriate control gains such that frequency restoration is achieved despite delays and active power sharing constraints. Simulations confirm the effectiveness of the proposed control strategy.